Authorities differed regarding the ruling on this hadith: be it sahih, hasan, or da’if. Some went the way of declaring it da’if. This would be Imam Nawawi’s view in Sharh al-Muhadhdhab and Sharh Sahih Muslim. Accordingly, it is the stance of the School’s later authorities.

Others, like Ibn Hibban, considered it sahih. And again others graded it hasan. Hafiz Munawi related that Ibn Hajar al-‘Asqalani assessed its lowest grade as hasan. (Fayd al-Qadir 1/113-14)

Ibn Hajar al-Haytami mentioned that the hadith is a proof that wearing a ring made of iron is disliked [makruh]. (al-Fatawa 1/262) Be that as it may, Imam Nawawi judged the aforementioned hadith to be weak; and thus, ruled that it is permissible to wear an iron ring, without it being disliked.

In conclusion, it is permissible to wear an iron ring, but better to avoid, as Ibn Hajar al-Haytami mentioned.